1. Technical Field
The present invention relates to an electrooptic device having a plurality of signal lines and driving circuits inside and outside the pixel array region, respectively, and more particularly, it relates to a technique for protecting the pixel array region and the driving circuits from static electricity flowing into the pixel array region.
2. Related Art
Electrooptic devices such as liquid crystal devices and organic electroluminescent devices have scanning lines and data lines passing through a pixel array region in which a plurality of pixels are arrayed. Electrooptic devices further have driving circuits such as a scanning-line driving circuit and a data-line driving circuit in positions next to the pixel array region. In such electrooptic devices, damage due to electrostatic discharge, that is, static damage sometimes occurs to damage the driving circuits during assembly, mounting a flexible board, or in use after shipment.
Thus, it is proposed to provide a protection circuit for protecting input lines to the driving circuits, output lines from the driving circuits, and power supply lines from static electricity (for example, refer to JP-A-2005-49637).
However, static electricity occurs in various portions of electrooptic devices. For example, when electrostatic discharge occurs in the pixel array region, the static electricity may flow into the scanning-line driving circuit along the scanning lines to cause static damage to the scanning-line driving circuit. Accordingly, it is desirable to provide a static protection circuit for the scanning lines. However, if electrooptic devices are decreased in size without reducing the area of the pixel array region, sufficient space for the protection circuit cannot often be provided between the pixel array region and the scanning-line driving circuit in recent years. Therefore, as shown in FIGS. 9A and 9B, a scanning-line driving circuit 104 and a protection circuit 105 are disposed on both sides of a pixel array region 10b and in the direction of the extension of scanning lines 3a. The protection circuit 105 has a structure in which diode devices 41 and 42 are electrically connected to each of the scanning lines 3a. Even if electrostatic discharge occurs in the position indicated by arrow and the static electricity enters the scanning line 3a, the protection circuit 105 with this structure can dissipate the static electricity to a high-potential power line 6s or a low-potential power line 6t via the diode device 41 or 42, respectively. It is preferable that the protection circuit 105 prevent damage to the diode devices 41 and 42 by reducing the static electricity flowing into the diode devices 41 and 42 with a diode-device protecting resistor 43 between the pixel array region 10b and the diode devices 41 and 42.
However, the structure shown in FIGS. 9A and 9B has the problem that, if electrostatic discharge occurs in a position close to the scanning-line driving circuit 104 as shown in FIG. 9A, most of the static electricity flows not to the protection circuit 105 but to the scanning-line driving circuit 104, causing static damage to the scanning-line driving circuit 104. This problem occurs also in the data lines 6a. 